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Study of the effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels by neutron scattering techniques.

Seong BS, Cho YR, Shin EJ, Kim SI, Choi SH, Kim HR, Kim YJ - J Appl Crystallogr (2008)

Bottom Line: In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures.The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates.Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

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ABSTRACT
Small-angle neutron scattering (SANS) and neutron powder diffraction (ND) techniques were used to study quantitatively the effect of nano-sized precipitates and boron addition on the mechanical properties of low-carbon steels. SANS was used to evaluate nano-sized precipitates, smaller than about 600 A in diameter, and ND was used to determine the weight fraction of the cementite precipitates. Fine core-shell structured spherical precipitates with an average radius of ~50 A, such as MnS and/or CuS, surrounded by BN layers were observed in the boron-added (BA) low-carbon steels; fine spherical precipitates with an average radius of ~48 A were mainly observed in the boron-free (BF) low-carbon steels. In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures. The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates. Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

No MeSH data available.


Effects of the rolling temperature on the mechanical properties of the low-carbon steel: (a) yield strength and (b) uniform elongation.
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fig4: Effects of the rolling temperature on the mechanical properties of the low-carbon steel: (a) yield strength and (b) uniform elongation.

Mentions: The effect of the hot-rolling temperature on the yield strength and uniform elongation of BF and BA steels is shown in Figs. 4 ▶(a) and 4 ▶(b), respectively. Boron addition decreases the yield strength and increases the uniform elongation. The yield strength and uniform elongation of the BF steels maintain nearly constant values with the hot-rolling temperature, whereas the yield strength of BA steels decreases drastically at a higher rolling temperature. Such dependency of the mechanical properties on the hot-rolling temperature for BA steels is suggested to be due to the different microstructural evolution and precipitation behaviour of these steels. The ferrite grains in the BA steels become coarse and irregular at a higher rolling temperature, as shown in Fig. 5 ▶, whereas the ferrite grains in the BF steels did not change significantly with the rolling temperature.


Study of the effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels by neutron scattering techniques.

Seong BS, Cho YR, Shin EJ, Kim SI, Choi SH, Kim HR, Kim YJ - J Appl Crystallogr (2008)

Effects of the rolling temperature on the mechanical properties of the low-carbon steel: (a) yield strength and (b) uniform elongation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2553556&req=5

fig4: Effects of the rolling temperature on the mechanical properties of the low-carbon steel: (a) yield strength and (b) uniform elongation.
Mentions: The effect of the hot-rolling temperature on the yield strength and uniform elongation of BF and BA steels is shown in Figs. 4 ▶(a) and 4 ▶(b), respectively. Boron addition decreases the yield strength and increases the uniform elongation. The yield strength and uniform elongation of the BF steels maintain nearly constant values with the hot-rolling temperature, whereas the yield strength of BA steels decreases drastically at a higher rolling temperature. Such dependency of the mechanical properties on the hot-rolling temperature for BA steels is suggested to be due to the different microstructural evolution and precipitation behaviour of these steels. The ferrite grains in the BA steels become coarse and irregular at a higher rolling temperature, as shown in Fig. 5 ▶, whereas the ferrite grains in the BF steels did not change significantly with the rolling temperature.

Bottom Line: In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures.The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates.Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
Small-angle neutron scattering (SANS) and neutron powder diffraction (ND) techniques were used to study quantitatively the effect of nano-sized precipitates and boron addition on the mechanical properties of low-carbon steels. SANS was used to evaluate nano-sized precipitates, smaller than about 600 A in diameter, and ND was used to determine the weight fraction of the cementite precipitates. Fine core-shell structured spherical precipitates with an average radius of ~50 A, such as MnS and/or CuS, surrounded by BN layers were observed in the boron-added (BA) low-carbon steels; fine spherical precipitates with an average radius of ~48 A were mainly observed in the boron-free (BF) low-carbon steels. In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures. The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates. Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

No MeSH data available.